code review 6307065: syscall: revert API changes in Windows Win32finddata fix.

src/pkg/syscall/ztypes_windows.go

 // Copyright 2011 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 package syscall
 
 const (
         // Windows errors.
         ERROR_FILE_NOT_FOUND      Errno = 2
         ERROR_PATH_NOT_FOUND      Errno = 3
@@ skipping 320 matching lines @@
         // convert into 100-nanosecond
         nsec /= 100
         // change starting time to January 1, 1601
         nsec += 116444736000000000
         // split into high / low
         ft.LowDateTime = uint32(nsec & 0xffffffff)
         ft.HighDateTime = uint32(nsec >> 32 & 0xffffffff)
         return ft
 }
 
-// Win32finddata is an incorrect struct definition, preserved for
-// backwards compatibility. Use Win32finddata1 and the
-// FindFirstFile1 and FindNextFile1 functions instead.
 type Win32finddata struct {
         FileAttributes    uint32
         CreationTime      Filetime
         LastAccessTime    Filetime
         LastWriteTime     Filetime
         FileSizeHigh      uint32
         FileSizeLow       uint32
         Reserved0         uint32
         Reserved1         uint32
         FileName          [MAX_PATH - 1]uint16
         AlternateFileName [13]uint16
 }
 
-type Win32finddata1 struct {
+// This is the actual system call structure.
+// Win32finddata is what we committed to in Go 1.
+type win32finddata1 struct {
         FileAttributes    uint32
         CreationTime      Filetime
         LastAccessTime    Filetime
         LastWriteTime     Filetime
         FileSizeHigh      uint32
         FileSizeLow       uint32
         Reserved0         uint32
         Reserved1         uint32
         FileName          [MAX_PATH]uint16
         AlternateFileName [14]uint16
 }
 
+func copyFindData(dst *Win32finddata, src *win32finddata1) {
+        dst.FileAttributes = src.FileAttributes
+        dst.CreationTime = src.CreationTime
+        dst.LastAccessTime = src.LastAccessTime
+        dst.LastWriteTime = src.LastWriteTime
+        dst.FileSizeHigh = src.FileSizeHigh
+        dst.FileSizeLow = src.FileSizeLow
+        dst.Reserved0 = src.Reserved0
+        dst.Reserved1 = src.Reserved1
+
+        // The src is 1 element shorter than dst. Zero that last one.
+        copy(dst.FileName[:], src.FileName[:])
+        dst.FileName[len(dst.FileName)-1] = 0

[brainman, 2012/06/09 12:15:31]

You should not override last char of FileName with 0. There could be real char
of the name there. As per your own comment:

// There is no loss of expressivity here, because the final
// uint16, if it is used, is supposed to be a NUL, and Go doesn't need that.

So, you should leave FileName as is without terminating 0. We use
syscall.UTF16ToString to convert it into string, it does not care if there is no
terminating 0.

+        copy(dst.AlternateFileName[:], src.AlternateFileName[:])
+        src.AlternateFileName[len(dst.AlternateFileName)-1] = 0

[brainman, 2012/06/09 12:15:31]

This line must be wrong. Why are you changing src? I think you should remove
that line as well.

+}
+
 type ByHandleFileInformation struct {
         FileAttributes     uint32
         CreationTime       Filetime
         LastAccessTime     Filetime
         LastWriteTime      Filetime
         VolumeSerialNumber uint32
         FileSizeHigh       uint32
         FileSizeLow        uint32
         NumberOfLinks      uint32
         FileIndexHigh      uint32
@@ skipping 522 matching lines @@
         REG_DWORD_BIG_ENDIAN
         REG_LINK
         REG_MULTI_SZ
         REG_RESOURCE_LIST
         REG_FULL_RESOURCE_DESCRIPTOR
         REG_RESOURCE_REQUIREMENTS_LIST
         REG_QWORD_LITTLE_ENDIAN
         REG_DWORD = REG_DWORD_LITTLE_ENDIAN
         REG_QWORD = REG_QWORD_LITTLE_ENDIAN
 )